Internet Engineering Task Force D. York
Internet-Draft Individual
Intended status: Informational T. Asveren
Expires: October 21, 2018 Ribbon Communications
April 19, 2018
P-Charge-Info - A Private Header Field (P-Header) Extension to the
Session Initiation Protocol (SIP)
draft-york-p-charge-info-07
Abstract
This text documents the current usage of P-Charge-Info, an existing
private Session Initiation Protocol (SIP) header field (P-Header)
used to convey billing information about the party to be charged.
This P-Header is currently used in production by several equipment
vendors and carriers and has been in usage since at least 2007. This
document is submitted to request the registration of this header
field with the Internet Assigned Numbers Authority (IANA).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 21, 2018.
Copyright Notice
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document authors. All rights reserved.
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to this document. Code Components extracted from this document must
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Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Purpose of this Document . . . . . . . . . . . . . . . . . . 3
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Alternatives . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. P-Charging-Vector . . . . . . . . . . . . . . . . . . . . 4
5.2. P-DCS-Billing-Info . . . . . . . . . . . . . . . . . . . 4
5.3. P-Asserted-Identity . . . . . . . . . . . . . . . . . . . 5
6. The P-Charge-Info Header . . . . . . . . . . . . . . . . . . 6
6.1. Applicability Statement for the P-Charge-Info header
field . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.2. Usage of the P-Charge-Info header field . . . . . . . . . 6
6.2.1. Procedures at the UA . . . . . . . . . . . . . . . . 6
6.2.2. Procedures at the Proxy . . . . . . . . . . . . . . . 7
6.3. Example of Usage . . . . . . . . . . . . . . . . . . . . 7
7. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8.1. Header Field . . . . . . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9.1. Trust Relationship . . . . . . . . . . . . . . . . . . . 8
9.2. Untrusted Peers . . . . . . . . . . . . . . . . . . . . . 9
9.2.1. Ingress from Untrusted Peers . . . . . . . . . 9
9.2.2. Egress to Untrusted Peers . . . . . . . . . . 9
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
11. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
12.1. Normative References . . . . . . . . . . . . . . . . . . 14
12.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Overview
In certain network configurations, several network entities have
found it useful to decouple the identity of the caller (what is
normally thought of as "Caller ID") from the identity/number used for
billing purposes. This document records the current usage of P-
Charge-Info, a private SIP header field, to provide simple billing
information and requests the registration of this header field with
IANA as required by Section 4 of [RFC5727].
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In a typical configuration, the identity of the caller, commonly
referred to as "Caller ID" by end users, is derived from one of the
following SIP header fields:
o P-Asserted-Identity
o From (in the absence of P-Asserted-Identity)
(NOTE: Some service providers have also used the Remote-Party-ID
header field but this was never standardized and was replaced by P-
Asserted-Identity in [RFC3325].)
This identity/number is typically presented to the receiving user
agent (UA) where it is usually displayed for the end user. It is
also typically used for billing purposes by the network entities
involved in carrying the session.
However, in some network configurations the "Caller ID" presented to
the receiving UA may be different from the number to be used for
billing purposes.
In this case, there exists a need for a way to pass an additional
billing identifier that can be used between network entities in order
to correctly bill for services.
Several carriers, application providers, and equipment providers have
been using the P-Charge-Info header field since at least 2007 as a
simple mechanism to exchange this billing identifier.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Purpose of this Document
This document has been prepared to document the existing deployed
usage of the P-Charge-Info header field and to comply with Section 4
of [RFC5727] to register this header field with IANA. It is noted
that RFC 5727 specifically deprecates new usage of "P-" header
fields, but P-Charge-Info has been in deployment since prior to 2007
and pre-dates RFC 5727. Given this, the authors request that P-
Charge-Info be admitted as a "grandfathered case" per Section 4 of
RFC 5727.
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4. Use Cases
The simplest use case for P-Charge-Info is an enterprise environment
where each SIP endpoint has a direct number that is passed by the
enterprise SIP proxy across to a SIP proxy at a SIP service provider
who provides connectivity to the Public Switched Telephone Network
(PSTN). Rather than cause the SIP service provider to have to track
each individual direct number for billing purposes, the enterprise
SIP proxy sends in the P-Charge-Info header field a single billing
identifier that the SIP service provider uses for billing purposes.
As another example, a hosted telephony provider or hosted voice
application provider may have a large SIP network with customers
distributed over a very large geographic area using local market PSTN
numbers but with only a very few actual PSTN interconnection points.
The customers may all have local phone numbers yet outgoing calls are
actually routed across a SIP network and out specific PSTN gateways
or across specific SIP connections to other SIP service providers.
The hosted provider may want to pass a billing identifier to its SIP
service providers either for the purpose of simplicity in billing or
to obtain better rates from the SIP service providers.
5. Alternatives
5.1. P-Charging-Vector
P-Charging-Vector is defined in Section 4.6 of [RFC7315] and used by
the 3GPP to carry information related to the charging of a session.
There are, however, some differences in the semantics associated with
P-Charging-Vector and P-Charge-Info. P-Charging-Vector is mainly
used to carry information for correlation of multiple charging
records generated for a single session. On the other hand, P-Charge-
Info is used to convey information about the party to be billed for a
call. Furthermore, P-Charging-Vector has a mandatory icid-value
parameter that is a globally unique value to identify the session for
which the charging information is generated. Such a globally-unique
identifier is not necessary when carrying information about the user
to be billed when it is attached to the corresponding session-related
signaling.
5.2. P-DCS-Billing-Info
P-DCS-Billing-Info is defined in Section 7 of [RFC5503] and used for
passing billing information between trusted entities in the
PacketCable Distributed Call Signaling Architecture. For many
billing situations, particularly the very large-scale residential
telephone networks for which this header field is designed, P-DCS-
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Billing-Info is an excellent solution. However, this ability to
address a range of situations adds complexity. According to RFC
5503, the following information is mandatory to include in each use
of the P-DCS-Billing-Info header field:
o Billing-Correlation-ID, a globally unique identifier
o Financial-Entity-ID
o RKS-Group-ID (record keeping server)
and may include a variety of additional parameters.
While this may work well in many billing scenarios, there are other
billing scenarios that do not need this level of complexity. In
those simpler scenarios all that is needed is simply a number to use
for billing. P-Charge-Info provides this simple solution for simple
billing scenarios.
Additionally, according to Section 7.3 of RFC 5503, it is mandatory
for a UA to create a Billing-Correlation-ID and insert this into the
P-DCS-Billing-Info header field (along with the other required
information) sent in the initial SIP INVITE. This again makes sense
for the residential telephone service environment for which this
header field is designed. In contrast, P-Charge-Info is designed to
be used among proxies and not to be used at all by normal user
agents. (P-Charge-Info may, though, be used by user agents
associated with PSTN gateways.)
5.3. P-Asserted-Identity
Early reviewers of this document asked why the P-Asserted-Identity
header field documented in [RFC3325] could not be used. As mentioned
in the use case example above, P-Asserted-Identity is used to
indicate the identity of the calling party. However, in this
instance, the requirement is to provide an additional identity of the
SIP-to-PSTN interconnect point.
It would be typical to find both P-Asserted-Identity and P-Charge-
Info used in a SIP exchange. P-Asserted-Identity would be used to
provide the caller identity which would be displayed to the end user
as "Caller ID" while P-Charge-Info would provide the billing
identifier used for the billing associated with the call.
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6. The P-Charge-Info Header
6.1. Applicability Statement for the P-Charge-Info header field
The P-Charge-Info header field is applicable within a single private
administrative domain or between different administrative domains
where there is a trust relationship between the domains.
6.2. Usage of the P-Charge-Info header field
The P-Charge-Info header field is used to convey information about
the identity of the party to be charged. The P-Charge-Info header
field is typically inserted into a SIP request, usually an INVITE, by
one of the following:
o the SIP proxy on the originating network;
o a PSTN gateway acting as a SIP UA; or
o an application server generating billing information.
P-Charge-Info is to be used by the SIP entity that provides billing
services for a session. This could be an entity generating billing
records or an entity interacting with another enitity generating
billing records. Upon receipt of an INVITE request with the P-
Charge-Info header field, such an entity SHOULD use the value present
in P-Charge-Info as indicating the party responsible for the charges
associated with the session.
6.2.1. Procedures at the UA
The P-Charge-Info header field may be inserted by PSTN gateways or
application servers acting as a SIP UA.
The P-Charge-Info header field is ignored by an end-user UA and
should not normally be received by such a UA. It MUST NOT be sent to
such a UA and the UA SHOULD ignore it if it receives the header
field. Similarly, an end-user UA originating a SIP message SHOULD
NOT insert this header field.
A PSTN gateway or application server acting as a UA MAY use the
content of the P-Charge-Info header field present in an INVITE
request it received for billing related procedures, e.g. in a billing
record or during interaction with another entity generating billing
records, as the identity of the party to be charged for the session.
A PSTN gateway or application server acting as a UA MAY use the
content of the P-Charge-Info header field to populate information
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about the identity of the party to charge in another type of
signaling, e.g. ISUP.
6.2.2. Procedures at the Proxy
A SIP proxy that supports this extension and receives a request,
typically a SIP INVITE, without the P-Charge-Info header field MAY
insert a P-Charge-Info header field. The contents of the inserted
header field may be decided based on local policy or by querying an
external entity to determine the identity of the party to be charged.
A proxy MAY use the content of the P-Charge-Info header field present
in an INVITE request it received for billing related procedures, e.g.
in a billing record or during interaction with another entity
generating billing records.
A SIP proxy that does not support this extension will pass any
received P-Charge-Info header field unmodified in compliance with RFC
3261.
A proxy supporting this extension SHOULD remove the P-Charge-Info
header field before sending a request to a UA that is not acting as a
PSTN gateway or appropriate application server.
6.3. Example of Usage
The content of the P-Charge-Info header field is typically just a SIP
URI used as a billing indicator. An example could be as simple as
one of:
P-Charge-Info:
P-Charge-Info:
P-Charge-Info:
P-Charge-Info:
Any other applicable SIP URI could be used.
7. Formal Syntax
This RFC contains the definition of one or more SIP header fields
that allow choosing between addr-spec and name-addr when constructing
header field values. As specified in [RFC8217], the "addr-spec" form
MUST NOT be used if its value would contain a comma, semicolon, or
question mark.
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The Private Header Field specified in this document is described in
both prose and an augmented Backus-Naur Form (BNF) defined in
[RFC5234]. Further, several BNF definitions are inherited from SIP
and are not repeated here. Implementors need to be familiar with the
notation and contents of [RFC3261] and [RFC5234] to understand this
document.
The syntax of the P-Charge-Info header field is described as follows:
P-Charge-Info = "P-Charge-Info" HCOLON (name-addr / addr-spec)
; name-addr and addr-spec are specified in RFC 3261
The SIP URI contained in the name-addr/addr-spec is the billing
indicator that is passed between the parties.
8. IANA Considerations
This specification registers a new proprietary SIP header field
according to the procedures defined in [RFC5727].
8.1. Header Field
The header field described in Section 7 is registered in the "Header
Fields" sub-registry of the "Session Initiation Protocol (SIP)
Parameters" registry by adding a row with these values:
Header Field Name: P-Charge-Info
Compact Form: none
Reference: [TBD: This document]
9. Security Considerations
9.1. Trust Relationship
Given that the information contained in the P-Charge-Info header
field will be used for billing purposes, the proxies and other SIP
entities that share this information MUST have a trust relationship.
If an untrusted entity were inserted between the trusted entities, it
could potentially interfere with the billing records for the call.
If the SIP connections are not made over a private network, a
mechanism for securing the confidentiality and integrity of the SIP
connection SHOULD be used to protect the information. One such
mechanism could be TLS-encryption of the SIP signaling stream.
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9.2. Untrusted Peers
9.2.1. Ingress from Untrusted Peers
If the P-Charge-Info header field was accepted by a SIP entity from
an untrusted peer, there is the potential for fraud if the untrusted
entity sent incorrect information, either inadvertently or
maliciously.
Therefore a SIP entity MUST remove and ignore the P-Charge-Info
header field when it is received from an untrusted entity.
9.2.2. Egress to Untrusted Peers
If the P-Charge-Info header field was sent by a SIP entity to an
untrusted peer, there is the potential exposure of network
information that is internal to a trust domain. For instance, the
untrusted entity may learn the identities of public SIP proxies used
within the trust domain which could then potentially be directly
attacked.
If an implementation does not strip P-Charge-Info from the message
where specified in this document, it introduces serious privacy
risks. Examples include revealing third-party billing relationships
that might be sensitive, as well as unmasking the identity of callers
who wish to remain anonymous. Depending on circumstances, the latter
case may result in unwanted harassment and even physical harm to the
calling party.
Therefore a SIP entity MUST remove the P-Charge-Info header field
when it is sent to an untrusted entity.
10. Acknowledgements
The authors thank the following people for their comments: Keith
Drage, Miguel Garcia, Sumit Garg, John Haluska, Juha Heinanen,
Christer Holmberg, Paul Kyzivat, Adam Roach, Jonathan Rosenberg,
Henning Schulzrinne, Tom Taylor and Glen Wang.
11. Changes
NOTE TO RFC EDITOR - Please remove this "Changes" section prior to
publication. Thank you.
Revision -07 incorporates significant feedback from Jean Mahoney
including:
o Updating references to obsolete RFCs;
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o Updating IANA considerations section;
o Changing example phone numbers; and
o multiple editorial and proofreading updates.
Revision -06 fixes one nit and updates the Requirements Language to
comply with BCP 14 / RFC 8174.
Revision -05 fixed a few typos and had other editorial changes.
Revision -04 removes the PASSporT and RFC 8224/8225 references
(inserted in Revision -03), as it was decided to capture that usage
in a separate draft.
Revision -03 incorporates feedback from the expert review by Adam
Roach, including:
o changing all references to "header" to be "header field";
o the addition of references to RFCs 8224 and 8225 related to STIR;
o a reference to RFC 8217 in the formal syntax; and
o multiple editorial and proofreading updates.
Revision -02 incorporates a range of feedback provided by Henning
Schulzrinne.
Revision -01 is a refresh as -00 expired. The affiliation of Tolga
Asveren was changed to Ribbon Communications.
Revision -00 strips out the NPI and NOA parameters to focus only on
the usage in a pure SIP-to-SIP environment. Multiple editing changes
were made for readability.
NAME CHANGE - The document is now "draft-york-p-charge-info" to
reflect the fact that the publishing route for the draft is being
determined.
Revision -06 updates the text for 2017 and changes Dan York's
affiliation to "Individual".
Revision -05 is a refresh as -04 expired. Several small tweaks were
also made to narrative text.
Revision -04 is purely a refresh as -03 expired.
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Revision -03 is purely a refresh as -02 expired.
Revision -02 is purely a refresh as -01 expired. My hope is to move
this document forward soon to put closure on it.
Revision -01 is purely a refresh as -00 expired. Only a few minor
tweaks to this "Changes" section of the document.
Revision -00 is the initial release of "draft-york-dispatch-p-charge-
info" and is identical to "draft-york-sipping-p-charge-info-15"
except for changes to wording to reflect the change to the DISPATCH
working group. The "organization" name for Dan York was also changed
from blank to "DisTel Research" to remove the confusion that it
looked like he was also employed by Sonus Networks.
NAME CHANGE - The document is now "draft-york-dispatch-p-charge-info"
to reflect the fact that the SIPPING Working Group no longer exists.
Revision -15 simply fixes a wording error in the abstract in the
previous revision. This will also be the last version of 'draft-
york-sipping-p-charge-info'. The next version will be 'draft-york-
dispatch-p-charge-info'.
Revision -14 incorporates the following changes:
o Two examples were updated to include a "+1" at the beginning of
the SIP URI.
o An example was changed to use "example.net" to be compliant with
RFC 2606.
o Dan York's organization was updated to "Individual" (from empty)
to indicate that his involvement with this draft is purely as an
individual with no connection to his employer.
o The length of time the header has been used in the Introduction
was changed to 7 years, to reflect the first usage around 2005.
o A note was added to the abstract indicating that this is expected
to be the last version using the name 'draft-york-sipping-p-
charge-info'.
o Informative references were added to RFC 3261 and RFC 2234 to
address missing references in the text.
o Numerous other tweaks to the text for readability.
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Revision -13 has no changes to content and was issued as -12 expired.
Discussions are under way coming out of IETF 83 on a plan to move
this draft forward. As the SIPPING working group no longer exists,
the draft name needs to change and there are a couple of other
required changes.
Revision -12 included the following modifications based on feedback
from John Haluska and Glen Wang:
o Modification of Appendix B to reflect ANSI T1.113 values.
Revision -11 represents a fairly significant revision responding to a
solid review by Paul Kyzivat and providing additional explanation. A
major shift was the move to using decimal values for the npi-value
parameter versus the text values of previous drafts. Changes
include:
o ABNF definition updated to indicate that npi is now a number vs
text.
o The "npi" and "noa" acronyms were expanded and stated near the
formal syntax definition.
o New section created explicitly mentioning the optional parameters.
o Example of optional parameters updated to have npi use a number vs
text.
o Appendix B added to give examples of NOA parameter.
o Overview text updated to indicate that P-Charge-Info was been in
use now for over 5 years (given that the draft has been in
development for 3 years).
o Several small fixes for readability.
Revision -10 included the following modifications:
o Formal ABNF definition updated.
o In formal syntax, semicolons added to npi-param and noa-param
definitions.
o npi-param changed to a 'gen-value' to use digits vs text. Values
npi-param are shown in Appendix A.
o Corrected example to show proper use of parameters.
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o Updated references to RFC 3427 and RFC 3968 to reference RFC 5727.
Revision -09 included the following modifications:
o Re-submitted with only a date change. Discussions are ongoing to
finalize this draft and submit it for expert review.
Revision -08 included the following modifications:
o The ABNF for the "npi-value" was modified to conform to the
sequence of possible values stated in ANSI T1.113.
o An Appendix A was created listing the values from ANSI T1.113.
Revision -07 was updated to the "trust200902" IPR statement and added
references to RFC 3968. At this point all comments have been
incorporated and publication will be requested.
Revision -06 had only a minor correction to the second usage example.
The IPR statement was also updated to comply with RFC 5378.
Revision -05 included the following modifications:
o The usage of P-Charge-Info for carrying the ISUP Charge Number
parameter was formally incorporated into the draft. Previous
revisions had mentioned it as a possible use case but had not
really explicitly included it.
o The examples/use cases section was expanded to include further
examples of where P-Charge-Info may be used.
o The original use case which discussed inter/intra-state billing
practices was changed as the geographical references were clouding
the more fundamental issue.
o The "UNKNOWN" value was added to the ABNF for the "npi-value"
parameter as that was identified as missing but required for ISUP
interworking.
o The optional "Nature of Address" parameter was added to support
interworking with the ISUP Charge Number.
Revision -04 corrected a major error in the example where the
parameter was placed inside the angle brackets. The P-DCS-Billing-
Info header was also added as an alternative and a few minor edits
were made.
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12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
.
[RFC5727] Peterson, J., Jennings, C., and R. Sparks, "Change Process
for the Session Initiation Protocol (SIP) and the Real-
time Applications and Infrastructure Area", BCP 67, RFC
5727, March 2010.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, .
12.2. Informative References
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/
RFC5234, January 2008, .
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private
Extensions to the Session Initiation Protocol (SIP) for
Asserted Identity within Trusted Networks", RFC 3325,
November 2002.
[RFC5503] Andreasen, F., McKibben, B., and B. Marshall, "Private
Session Initiation Protocol (SIP) Proxy-to-Proxy
Extensions for Supporting the PacketCable Distributed Call
Signaling Architecture", RFC 5503, DOI 10.17487/RFC5503,
March 2009, .
[RFC7315] Jesske, R., Drage, K., and C. Holmberg, "Private Header
(P-Header) Extensions to the Session Initiation Protocol
(SIP) for the 3GPP", RFC 7315, DOI 10.17487/RFC7315, July
2014, .
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[RFC8217] Sparks, R., "Clarifications for When to Use the name-addr
Production in SIP Messages", RFC 8217, DOI 10.17487/
RFC8217, August 2017, .
Authors' Addresses
Dan York
Individual
Keene, NH
USA
Email: dyork@lodestar2.com
Tolga Asveren
Ribbon Communications
NJ
USA
Email: tasveren@rbbn.com
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